Predetermined torque release wrench

ABSTRACT

A predetermined torque release wrench which may be used to apply a torque to a fastener. The wrench includes an arm connected to the ratchet head of the wrench with a variable spring set cam lever arrangement. The cam lever is pivoted in the wrench case. The arm overcomes the resistance of the cam lever when a predetermined torque is reached.

United States Patent [191 11 3,839,928 Bergquist Oct. 8, 1974.

[ 1 PREDETERMINED TORQUE RELEASE WRENCH FOREIGN PATENTS OR APPLICATIONS209,452 5/1957 Australia 81/52.4 109,874 12/1939 Australia 81/524297,924 4/1954 Switzerland 8l/52.4

Primary Examiner-James L. Jones, Jr.

Attorney, Agent, or Firm-Walter C. Vliet; David W.

Tibbott [5 7] ABSTRACT A predetermined torque release wrench which maybe used to apply a torque to a fastener. The wrench includes an armconnected to the :ratchet head of the wrench with a variable spring setcam lever arrangement. The cam lever is pivoted in the wrench case.

The arm overcomes the resistance of the cam lever when a predeterminedtorque is reached.

4 Claims, 6 Drawing Figures 1 PREDETERMINED TORQUE RELEASE WRENCHBACKGROUND OF THE INVENTION This invention relates to torque wrenchesand more particularly to a predetermined torque release wrench which maybe used to apply a torque to a fastener.

A major concern with all torque wrenches is accuracy and repeatability.The wrench must release at the desired torque under all conditions. Theprior art has taught various cam release mechanisms which freely act onand are restrained by a spring loaded plunger.

The accuracy of the prior art wrenches was therefore dependent on thefree movement of the spring loaded plunger. It was soon determined thatby nature of the cam release mechanisms used a side load as well as anaxial load was transmitted to the plunger. Various devices such as ballbearings were used to minimize the side wall friction developed. Thesedevices have proved only partially satisfactory and are subject tovariations if foreign matter is present.

SUMMARY OF INVENTION It is therefore the primary object of thisinvention to provide a novel torque wrench which has a high degree ofaccuracy and repeatability by minimizing the side load transmitted'tothe spring loaded plunger by the cam release mechanism.

The foregoing and other objects will be carried out by providing atorque wrench comprising: a handle; a work engaging member rotatablymounted on said handle; an arm operatively connected at one end to saidwork engaging member and longitudinally extending along said handle andadapted to rotate relative to said handle; a cam lever means forreleasably restraining said arm away from rotating relative to saidhandle, said cam lever being substantially restrained by said handle indirections perpendicular to the longitudinal axis and substantially freeto move longitudinally; a resilient means for urging said cam lever insaid longitudinal direction towards the position of restraining said armfrom rotation.

BRIEF DESCRIPTION OF DRAWINGS FIG. l is a sectional view of a torquewrench constructed in accordance with the present invention and shownprior to release.

FIG. IA is a continuation of FIG. 1.

FIG. 2 is a plan view of the work head of the present invention.

FIG. 3 is a sectional view taken along line 33 of FIG. 1.

FIG. 4 is a sectional view taken along line 4-4 of FIG. 1.

FIG. 5 is a fragmentary sectional view of the wrench showing the areawherein the invention lies after release.

DESCRIPTION OF THE PREFERRED EMBODIMENT The operation and description ofthe invention in the form of the preferred embodiment shown in thedrawings may best be understood by referring to FIG. 1 for generalassembly and for operation of the related parts. In general, the wrenchof the present invention is substantially identical to that shown in US.Pat. No. 3,577,815 issued to Clifford A Bergquist except that it iscapable of torque response in one direction and is provided with aunique cam lever means which minimizes the side thrust applied to thetorque spring plunger and is the subject of this invention.

Referring to the drawing, there is shown a torque wrench which includesa tubular handle 1. A work head, generally indicated at 2 is rotatablymounted on the handle 1. The work engaging member 2 is shown in the formof a ratchet head including a stud 3 and a lever 4 for reversing thedirection of torque transmission. The head is conventional and need notbe described in detail.

An arm 5 has one end fixed to the work engaging member 2 and extendslongitudinally into the handle I. The arm 5 and hence the work head 2are pivotably connected to the handle 1 by means of pivot pin 6. A pairof bearing balls 8 are provided for aiding of the swinging movement ofarm 5. The other end of arm 5 is cut off at an angle other thanperpendicular to the longitudinal axis of the arm and provided with ahardened contact pin 9. The cut off angle is selected to assure contactof contact pin 9 with cam lever 10. Cam lever 10 is mounted to thehandle 1 by means of cam pin 11 and cam housing 12. Rotation of camlever 10 is resisted by contact with a plunger 15 which is slidablymounted in handle 1 and positioned on the opposite side of cam lever 10from arm 5. 'Calibration screw 16 adjusts the initiation contact pointon the cam lever and is utilized to calibrate the wrench release point.

The end of the tubular handle 1 opposite work head 2 is identical tothat shown in US. Pat. No. 3,577,815 and is numbered identically herefor ease of reference. The spring acts between the cylindrical member 30and hence the handle 1, and the plunger 15 to urge the plunger 15 towardthe cam lever 10 and arm 5.

When the wrench is in use, a torque will be applied to the stud 3 andwork engaging member 2 which tends to rotate the arm 5 relative to thehandle 1. The arm 5 is prevented from rotating relative to the handle 1by cam lever 10. As increased torque is applied, contact pin 9 exertsincreased force on cam lever 10. The force tends to cam or rotate camlever 10 about cam pin 11. The rotation of cam lever 10 is resisted bycontact with plunger 15 which in turn is resiliently urged in contactwith the cam lever 10 by spring 40.

The force of spring 40 is adjustable by means of sleeve 21 suitablythreaded 20 which when rotated as described in U.S. Pat. No. 3,577,815adjusts the tension of spring 40 which determines the degree ofresistance to rotation of cam lever 10 and hence the torque which may beapplied to stud 3 before the cam lever 10 is rotated out of the way ofarm 5. When the applied torque exceeds the amount required to displaceor rotate the cam lever 10, arm 5 will rotate within the handie 1causing it to strike a blow on the handle 1. The blow is the signal tothe operator that the predetermined torque on stud 3 has been exceeded.

The advantage of using a cam lever attached to the handle as opposed tohaving the arm 5 cam directly against plunger 15 can best be appreciatedby viewing FIG. 5. By selection of the cam pin 11 centerline location onthe cam lever 10 point of contact line it will be obvious to thoseskilled in the art that the force applied to the plunger 15 by cam lever1l0 will be essentially axial for nominal rotation of the cam lever.Side load forces will be taken in cam pin 11 resulting in rotationalfriction in cam pin 11 as opposed to undesirable sliding frictionbetween the plunger and handle 1 as in the case of prior art.

From the foregoing, it is apparent that the objects of this inventionhave been carried out. Sidewise forces on the spring plunger have beenminimized by the unique cam lever of this invention. While the torquewrench of the present embodiment will indicate or have a predeterminedtorque release in one direction only, it is possible to construct atwo-way wrench utilizing the present invention by use of double cams inopposite relationship or other similar use of intermediate cammingmeans.

It will be understood that the embodiment shown is for illustrativepurposes and that various modifications and variations in the presentinvention may be effected without departing from the spirit and scope ofthe novel concept presented here.

I claim:

1. A torque wrench comprising:

a handle;

a work engaging member rotatably mounted on said handle;

an arm operatively connected at one end to said work engaging member andlongitudinally extending along said handle and adapted to rotaterelative to said handle;

a cam lever means secured by a radially fixed pivot pin to the handlefor releasably restraining said arm away from rotation relative to saidhandle;

a resilient means for urging said cam lever means towards the positionof restraining said arm from rotation;

said cam lever means being in point contact with said resilient means ina plane extending substantially perpendicular to the axis of said armand through said pivot pin so as to impart a thrust on said resilientmeans acting generally parallel to the axis of said arm; and

said arm is in sliding point contact with a surface of said cam levermeans, said surfaces being shaped to provide greater leverage betweensaid arm and cam lever once the cam lever means begin to pivot in thedirection of said resilient means thereby allowing the arm to move moreeasily.

2. A torque wrench comprising: a hollow handle; a work engaging memberrotatably mounted on said handle; an arm operatively connected at oneend to said work engaging member and longitudinally extending into saidhandle and adapted to rotate relative to said handle;

a plunger longitudinally movable in said handle and positioned oppositethe other end of said arm;

resilient means for urging said plunger towards said arm;

cam lever means intermediate said arm and said plunger for releasablyrestraining said arm away from rotating relative to said handle, saidcamming means being substantially restrained by said handle in radialdirections about a point of rotation and substantially free to rotateabout said point;

said cam lever means being in point contact with said resilient means ina plane extending substantially perpendicular to the axis of said armand through said pivot pin so as to impart a thrust on said resilientmeans acting generally parallel to the axis of said arm; and

said arm is in sliding point contact with a surface of said cam levermeans, said being shaped to provide greater leverage between said armand cam lever once the cam lever means begin to pivot in the directionof said resilient means thereby allowing the arm to move more easily. 3.The torque wrench of claim 2 wherein said cam lever means comprises acam lever secured by fixed pivot pin to said handle.

4. The torque wrench of claim 3 wherein said cam lever is pivotablyrotated about a point substantially lying on a line radial to the pointof contact between said plunger and said cam lever such that radialforces created by said camming of said arm against said lever areabsorbed by said pivot means and circumferential forces beingsubstantially axial in directions relative to said handle and saidplunger are absorbed by said

1. A torque wrench comprising: a handle; a work engaging memberrotatably mounted on said handle; an arm operatively connected at oneend to said work engaging member and longitudinally extending along saidhandle and adapted to rotate relative to said handle; a cam lever meanssecured by a radially fixed pivot pin to the handle for releasablyrestraining said arm away from rotation relative to said handle; aresilient means for urging said cam lever means towards the position ofrestraining said arm from rotation; said cam lever means being in pointcontact with said resilient means in a plane extending substantiallyperpendicular to the axis of said arm and through said pivot pin so asto impart a thrust on said resilient means acting generally parallel tothe axis of said arm; and said arm is in sliding point contact with asurface of said cam lever means, said surfaces being shaped to providegreater leverage between said arm and cam lever once the cam lever meansbegin to pivot in the direction of said resilient means thereby allowingthe arm to move more easily.
 2. A torque wrench comprising: a hollowhandle; a work engaging member rotatably mounted on said handle; an armoperatively connected at one end to said work engaging member andlongitudinally extending into said handle and adapted to rotate relativeto said handle; a plunger longitudinally movable in said handle andpositioned opposite the other end of said arm; resilient means forurging said plunger towards said arm; cam lever means intermediate saidarm and said plunger for releasably restraining said arm away fromrotating relative to said handle, said camming means being substantiallyrestrained by said handle in radial directions about a point of rotationand substantially free to rotate about said point; said cam lever meansbeing in point contact with said resilient means in a plane extendingsubstantially perpendicular to the axis of said arm and through saidpivot pin so as to impart a thrust on said resilient means actinggenerally parallel to the axis of said arm; and said arm is in slidingpoint contact with a surface of said cam lever means, said being shapedto provide greater leverage between said arm and cam lever once the camlever means begin to pivot in the direction of said resilient meansthereby allowing the arm to move more easily.
 3. The torque wrench ofclaim 2 wherein said cam lever means comprises a cam lever secured byfixed pivot pin to said handle.
 4. The torque wrench of claim 3 whereinsaid cam lever is pivotably rotated about a point substantially lying ona line radial to the point of contact between said plunger and said camlever such that radial forces created by said camming of said armagainst said lever are absorbed by said pivot means and circumferentialforces being substantially axial in directions relative to said handleand said plunger are absorbed by said plunger.